Extracorporeal immunosorption therapy has drawn increased interest for clinical application to autoimmune and neoplastic diseases. However, no systematic study to delineate the reactions occurring during immunosorption treatment of plasma has been undertaken. A complete understanding of the phenomena must be attained if this technique is to be advanced in application to immune complex and antibody-mediated diseases. The objective of our research is to obtain a quantitative and fundamental physicochemical understanding of the interactions of immune complexes and other serum components with various immunoadsorbents. Our aims are to: (1)\understand the complex interactions in solution involving antigen, antibody, complement, and other plasma-borne molecules; (2)\define the reactions in solution between immune complexes and various receptor molecules that bind immunoglobulins, immune complexes, and/or complement components; and (3)\investigate the reactions occurring during immunosorption of immune complexes with a variety of receptor molecules (e.g., protein A, bovine conglutinum, human C1q) bound to solid supports. Our objectives for the coming year include: (1)\complete physicochemical and immunological characterization of monoclonal and polyclonal antibodies under study including, where applicable, determination of affinity constants, hydraulic radius, isoelectric point, and epitope specificity; (2)\further studies of IC size formation and redistribution using SDGC and QLS with monoclonal Abs and low-moderate affinity polyclonal Ab preparations; (3)\development of mathematical models describing IC formation between bivalent Abs and multivalent Ags for comparison with our experimental results; (4)\further analysis of naturally occurring IC, including separation of IC into their constituent components, characterization of all components, and determination of average apparent association constants of the respective Abs and Ags; (5)\construction of a minielectrophoresis cell that will allow QLS spectroscopy on IC as they move within an electric field. By focusing the beam at different points within the cell, a finer resolution of the parameters than that obtained using a stationary scattering solution (i.e., mean size) may be obtained; and (6)\preparation of a variety of immunoadsorbents including immobilized protein A, conglutinin, and C1q for studies during the third year on the effects of immunoadsorption on physicochemical properties of IC. (HF)